Sitting in her tiny room at a home for the elderly in the eastern Kazakh city of Semey, Matushkina remembers the days when the loud blasts of nuclear tests several hundred kilometres away frightened everyone.

A total of 456 nuclear tests were conducted at the test site over 42 years until Kazakhstan shut down the facility 20 years ago on August 29, 1991, making it the first country to voluntarily give up nuclear weapons.

“I was working in a medical institute, teaching chemistry. Almost every day, announcements on the radio at noon would say: ‘Now there is going to be a test of nuclear weapons.’ Everything would shake. The windows in my classroom were shattered by the shockwave from one of the blasts,” Matushkina said.

On August 29, 1949 at 7 am, the first Soviet nuclear bomb — named First Lightning — exploded in the steppe of eastern Kazakhstan, throwing up a huge mushroom cloud and dumping vast amounts of radioactive materials on the 1.5 million people living in the nuclear impact zone, which is the size of Belgium.

While the nuclear disaster at Ukraine’s Chernobyl and the bombing of Japan’s Hiroshima and Nagasaki are etched in the world’s memory, what happened at Semey, then known as Semipalatinsk, appears to be all but forgotten.

“Unfortunately, we only remember the problems of the damage caused by the testing site on anniversaries,” said Kazbek Apsalikov, the head of the Semey research centre of radiation medicine and ecology, a once-secret facility created to monitor the impact of radioactivity on the population.

The provincial and otherwise unremarkable town of Semey, whose name was changed four years ago, lies 150 kilometres (93 miles) west of the 18,400 square-kilometre (7,100 square-mile) nuclear testing site where the arms race between the Soviet Union and the United States began.

Under the cover of secrecy, the Soviet military built mock road and rail bridges and even apartment blocks at the site to study the impact of nuclear blasts. Their remains still stand as an eery reminder.

Ahead of nuclear tests, the Soviet military warned the public to shut windows and stay at home or remain inside buildings, witnesses recall.

But one of those who decided to peep out of curiosity was Suakysh Iskakova, 77, a resident at the same home as Matushkina, who says she paid for it with her eye-sight.

“When I was blinded from the blast, my uncle took me to see the doctor and the doctor said it was my own fault that I looked at the bright light from the explosion,” Iskakova said.

At the same site, in November 1955, the Soviets detonated their first hydrogen bomb, designed by physicist Andrei Sakharov, later to become a famous dissident.

In 1957, the Soviet authorities established a secret facility to monitor the impact of radiation on human life. Its now declassified documents describe the contamination of Kazakh villages with scientific meticulousness

“The village of S. was contaminated by radiation from precipitation after a 1953 nuclear test,” said one document from 1967, adding that radiation levels in the village were still ten times higher than normal.

Although the site has been shut down for 20 years, Kazakhstan is still reeling from the effects of long-term nuclear testing.

The Semipalatinsk region around the test site was subjected to the fallout from a total of 616 nuclear explosions over a period of 40 years.

The region has the highest cancer rate in the country, something that is at least partly attributable to the effects of fallout, said Apsalikov, the head of the national radiation research institute.

“How much longer the effects of the disaster will linger, we don’t know,” said Marat Sandybayev, the director of Semey’s brand-new oncology centre.

While it is hard to determine precisely how many have been affected by nuclear testing, scientists link the region’s higher rates of cancer and heart disease, especially among younger population, to the effects of radiation.

Officials at the Institute of Radiation Safety and Ecology in the once closed military city of Kurchatov, some 160 kilometres west of Semey, say they hope farmers will eventually be able to reclaim land at the test site.

The contamination at the site is scattered and levels have not changed significantly in the last 20 years, said Sergei Lukashenko, the director of the institute.

“The only way to remedy this contamination is to remove the upper layer of soil and store it in a secure place,” he said.

In spite of the contamination and its ecological and human consequences, many residents say they are still proud of the accomplishments of Soviet scientists and military during the Cold War.

“Back then, the tests were necessary, I think. People were simply doing their job,” said Svetlana, a Kurchatov resident, who declined to give her surname. “You know yourself what happened in Hiroshima and Nagasaki. We needed this at the time.”